feat(prelude): lambda capture

lispers-core/src/lisp/environment.rs

@@ -1,5 +1,5 @@
 use super::{expression::Expression, prelude::mk_prelude};
-use std::{cell::RefCell, collections::HashMap, rc::Rc};
+use std::{cell::RefCell, collections::HashMap, fmt::Display, rc::Rc};
 
 #[derive(PartialEq, Clone, Debug)]
 /// A Environment is a stack of `EnvironmentLayer`s. Each `EnvironmentLayer` is a mapping from
@@ -136,6 +136,30 @@ impl Default for Environment<'_> {
     }
 }
 
+impl Display for Environment<'_> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        if let Some(x) = &self.outer {
+            write!(f, "{}<{}", self.layer, x)
+        } else {
+            write!(f, "")
+        }
+    }
+}
+
+impl Display for EnvironmentLayer {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(
+            f,
+            "{{{}}}",
+            self.symbols
+                .iter()
+                .map(|(k, v)| format!("{}={}", k, v))
+                .collect::<Vec<_>>()
+                .join(", ")
+        )
+    }
+}
+
 #[test]
 fn test_environment() {
     let mut env = Environment::new();